In a conventional macro cellular system, the radius of a cell ranges from several hundreds of meters to several thousands of kilometers, and usually a user terminal is served by one cell. Meanwhile, in a cell, strength of received signals is different. According to different signal strength at the locations of user terminals, user terminals may be classified into two different types: user terminals located at a cell center and user terminals at a cell edge. The user terminals located at the cell center, due to good received signals and a high signal to interference plus noise ratio (Signal to Interference plus Noise Ratio, SINR), may receive a service transmitted at a high rate; the user terminals located at the cell edge can only receive the simplest service because the signals are poor and subject to interference of the signals of a neighboring cell and the service throughput is low. In an era of voice services only, the above macro cellular system may satisfy the basic requirement of a user, but with the development of new wireless services, such as wireless Internet, requirements on the wireless communication system capacity are higher and higher. The macro cellular system of a large radius cannot satisfy growing service requirements, and in particular, the requirements of anytime online services. Due to the existence of users at the cell edge, the overall service capacity is limited. Therefore, the cell radius becomes smaller with the increase of the service capacity. In hot areas (such as office buildings and central business districts), the cell radius is gradually reduced to about 50-100 meters. The conventional macro cell develops toward a smaller micro cell and a pico cell.
In addition, in the conventional cellular system, the height of an antenna is dozens of meters to one hundred meters, and the model of a cell may be simplified as an elliptical or hexagonal cell model. There are apparent differences between different cells. In the structure of a micro cell or a pico cell, and typically the coverage of an office building, to provide better services, a base station is placed at heights (for example, placed on a roof or tower, but this already cannot meet the requirements. The distribution of base stations is flat distribution, and the height may be a dozen meters or the distance between floors of a building. One user terminal UE may receive signals from N base stations nearby (several base stations or several dozens of base stations) (Base Stations, BSs), and the signals sent by the UE may also be received and processed by the N base stations nearby. In this case, the form of the base station changes, and may not be a base station with complete functions in the sense of a conventional macro cell, but a distributed mini base station, a distributed antenna over a fiber, a conventional wireless relay (Relay) station, or an amplifier, or may be different virtual base stations formed by the same base station through the beams of a smart antenna. These base stations may be uniformly referred to as wireless access nodes (Access Nodes, ANs).
One UE may receive service data sent by several BSs nearby, and the signals sent by one UE may be received by several BSs nearby. If multiple UEs in the system share the same channel resources (this is a common application scenario), great interference is caused between information that is sent to different UEs, and great interference is also caused to the uplink data that is sent by different UEs and received by the same BS. FIG. 1 is a schematic diagram of a conventional grid wireless access system. As shown in FIG. 1, when the BS_1 sends data to the UE_1 or receives data from the UE_1, interference may be caused to the UE_2 that uses the same channel to send or receive data. If the distance between different wireless access nodes is short, the interference problem is serious, and the normal work of the system is affected. The technologies used to solve inter-cell interference include interference randomization and interference cancellation, fractional frequency reuse (Fractional Frequency Reuse, FFR), multi-user MIMO (Multi-User MIMO), and so on. However, all these conventional solutions for solving inter-cell interference aim at a macro cell and cannot effectively reduce the interference in a grid wireless access system where the wireless access nodes in micro cells of a small radius are close to each other.